Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H182O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H182O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (∼3.5 × 10−4–7.5 × 10−4) than in the colder envelope (∼1.0 × 10−3–2.2 × 10−3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ∼105 yr after the infrared dark cloud stage.

BibTeX @article{Coutens2014,author={Coutens, A. and Vastel, C. and Hincelin, U and Herbst, E. and Lis, D.C. and Chavarría, L. and Gerin, M. and van der Tak, F. F. S. and Persson, Carina M. and Goldsmith, P.E. and Caux, E.},title={Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data},journal={Monthly notices of the Royal Astronomical Society},issn={0035-8711},volume={445},issue={2},pages={1299-1313},abstract={Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H182O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H182O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (∼3.5 × 10−4–7.5 × 10−4) than in the colder envelope (∼1.0 × 10−3–2.2 × 10−3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ∼105 yr after the infrared dark cloud stage.},year={2014},keywords={astrochemistry ISM: abundances ISM: individual objects: G34.26+0.15 ISM: molecules},}

RefWorks RT Journal ArticleSR ElectronicID 208828A1 Coutens, A.A1 Vastel, C.A1 Hincelin, UA1 Herbst, E.A1 Lis, D.C.A1 Chavarría, L.A1 Gerin, M.A1 van der Tak, F. F. S.A1 Persson, Carina M.A1 Goldsmith, P.E.A1 Caux, E.T1 Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI dataYR 2014JF Monthly notices of the Royal Astronomical SocietySN 0035-8711VO 445IS 2SP 1299OP 1313AB Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H182O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H182O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (∼3.5 × 10−4–7.5 × 10−4) than in the colder envelope (∼1.0 × 10−3–2.2 × 10−3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ∼105 yr after the infrared dark cloud stage.LA engDO 10.1093/mnras/stu1816LK http://publications.lib.chalmers.se/records/fulltext/208828/local_208828.pdfLK http://dx.doi.org/10.1093/mnras/stu1816OL 30